BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
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The invention relates to an installation path network for distribution areas having multiple subscriber stations arranged in a plurality of adjacent distribution areas.
DESCRIPTION OF RELATED ART
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Multiple subscriber stations serviced by a network of installation paths are known wherein the subscriber stations are interconnected to each other through subscriber lines within a distribution area emanating from a common distribution point for the distribution area. The entire system, which has a plurality of the distribution areas, is serviced from a center point with feeder lines connecting the distribution points for each of the distribution areas to the center point.
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A conventional system is shown and discussed in "A Study on Node Placement for Video Distribution Services and Optical Subscriber Loops" in the Technical Research Report CS90-3, published by the Institute of Electronics, Information and Communication Engineers in Japan. In the disclosed distribution system, the nodes are placed at the center of each distribution area, as shown in Figure 3 of the report. Such placement of the nodes is conventional, and the typical topology of an installation system requires that the distribution points or nodes for each distribution area be located in the center of the area.
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The installation path or route topology having a distribution point or node in the center of each distribution area has advantages directed to the distribution of information throughout each distribution area. The performance of such a system, however, is not only judged by its effective distribution of information throughout the distribution area, but also by the cost for installing the route system in order to implement the distribution of information throughout the surface area.
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Recently, the cost of the line or cable does not contribute to the greatest cost for installing the distribution network. The cost of the cable is being reduced as the result of mass-production, however, the cost of routing the cable or line throughout the distribution area is increasing due to labor costs. Each route that the cable or line follows requires an installation path for the route. Such installation paths are created by digging trenches or gutters for burying ducts or conduit through which the cable or line passes, erecting poles or stringing lines or cables between the poles for aerial route instruction, or just directly burying the line or cable. Recently, underground installation has been found to be more favorable in view of concerns about the environment and the aesthetics of aerial route installation.
SUMMARY OF THE INVENTION
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It is an object of the invention to reduce the cost of the cable installation by focusing on minimizing the length of the installation paths provided for in the construction of the distribution area. Preferably, a route topology that minimizes the construction cost per subscriber station by permitting installation paths or routes to share as many cables or lines as possible is achieved by the present invention.
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Figure 2 shows a conventional route topology for a service area having a plurality of subdivided and adjacent distribution areas. According to the conventional system shown in Figure 2, each distribution area is considered to be a square area of one unit dimension in length and width. The service area is subdivided into sixteen (16) distribution areas, each having sixteen (16) subscriber stations 5. The center point 1 of the service area provides a central distribution point for the distribution areas. Feeder lines 2 extend outwardly from the center point to reach each of the distribution areas. Within each distribution area, a centrally positioned distribution point 3 is provided. Subscriber lines 4 within the distribution area link each of the subscriber stations to the distribution point.
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An analysis of the route topology of the conventional installation network shown in Figure 2 shows that the total length of the installation paths can be determined from the subtotal lengths of the feeder line installation paths and the subscriber line installation paths with respect to the unit dimension represented by the length and width of each distribution area. As shown, there are five feeder lines 2, each extending for three units. Additionally, there are five subscriber lines 4 for each of the sixteen distribution areas, each extending 3/4 of one unit measure. The total installation path network, therefore, equals 75 measurement units, the significance of which will be discussed hereinafter with respect to the description of the preferred embodiments of the invention.
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It is an object of the invention to minimize the cost of installation for a network of installation paths within a distribution area by positioning the distribution point for the distribution area to be nearest to the center point for the service area. In particular, for rectangularly subdivided system areas, it is preferred to position the distribution point in a corner of each rectangularly shaped distribution area nearest to the center point for the system area.
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It is an object of the invention to minimize the total length of the installation path network by combining feeder and subscriber cables or lines in single installation paths within a plurality of the distribution areas for a system or service area that is serviced by the distribution system.
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It is an object of the invention to minimize the total length of the network of installation paths for the distribution system by providing a feeder line common to all subdivided distribution areas that extends in one direction through all such areas and connects together the distribution points for each of the distribution areas.
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It is an object of the invention to recognize that in the installation of a distribution system for multiple subscriber stations, some subscriber stations require immediate connection to the system, whereas other subscriber stations may be connected to the systems in the future, or not at all depending upon circumstances not known at the time of initially installing the distribution system.
BRIEF DESCRIPTION OF THE DRAWINGS
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Figure 1A - Figure 1C are diagrams of a network of installation paths for feeder and subscriber cables or lines according to the present invention.
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Figure 2 is a diagram of a conventional route topology of feeder and subscriber lines for a distribution system having a plurality of subdivided distribution areas.
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Figure 3A - Figure 3F each show different embodiments of a single distribution area having multiple subscriber stations with subscriber lines interconnecting the stations from a common distribution point.
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Figure 4A is a diagram showing a network of installation paths for feeder and subscriber lines or cables according to another embodiment of the present invention. Figure 4B is a diagram showing a single distribution area having multiple subscriber stations connected together by subscriber lines to a common distribution point. Figure 4C is a diagram similar to Figure 4B, but showing a modification of the subscriber line connection network within a distribution area.
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Figures 5A - 5G are diagrams showing the selective connection of subscriber stations to a common distribution point within a single distribution area, according to several modifications.
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Figure 6 is a diagram showing an embodiment of the installation path network for feeder and subscriber lines or cables according to the present invention.
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Figures 7A and 7B each show a diagram of selective connection of multiple subscriber stations within a single distribution area according to preferred embodiments of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
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Figure 1A is a diagram showing a distribution system or service area 10 subdivided into a plurality of distribution areas 15. Each of the distribution areas 15 has a plurality of subscriber stations 16, each denoted by an "X". Feeder lines 20 connect from a center point 12 of the system area to each of the distribution areas 15. Subscriber lines 25 connect each of the subscriber stations to a distribution point 22 along the feeder lines.
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In a typical system, both the feeder lines 20 and the subscriber lines 25 are fiber optic cables. In another system, the feeder lines 20 are fiber optic cables and the subscriber lines 25 are copper cables. In the latter system, each of the distribution points 22 is provided with a remote multiplexer. On the other hand, it is recognized that, in the practical sense, there may be some subscriber stations that are not used initially upon installation of the system or not at all over the life of the system. For purposes of explanation, however, it is assumed that each subscriber station in the system is to be connected.
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In order to install the route topology of the distribution system, the distribution lines, including the feeder lines and subscriber lines are either buried or strung aerially throughout the distribution system. Recently, buried distribution systems have found wide acceptance as a result of their compatibility with environmental and aesthetic concerns. Buried installation paths include the direct burial of the cable lines, or the burial of conduit or duct in trenches or gutters in the ground through which the cables or lines are routed. For aerial installation paths, the lines or cables are strung between poles or other type structures to implement the desired route topology.
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According to the object of the invention, the installation path network for the distribution lines is minimized by positioning the distribution points 22 for each of the subdivided distribution areas 15 nearest to the center point 12 for the distribution system area. In particular, the embodiments of the invention shown in Figures 1, 4 and 5 show that the distribution points 22 for each distribution area 15 are not in the center of the distribution area, as in the conventional route topology for distribution systems shown in Figure 2, for example, but are rather preferably in a position nearest to the center point 12.
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For purposes of illustration, the distribution areas 15 are considered to be square or rectangular, but they may take any shape in the application of such an installation of the system. Despite the shape of each of the subdivided areas, it is contemplated that there will be a distribution point in common with a subscriber station or superimposed on a subscriber station from the route topology point of view that is nearest to the center point 12 for the system.
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Figure 1A discloses a preferred embodiment of the invention. Sixteen distribution areas 15 are provided in the distribution system or service area shown in Figure 1A, but only the subscriber stations for the upper right quadrant of the system area are shown in detail. It is understood that a plurality of subscriber stations 16 exist in each of the distribution areas 15 even though they are not shown.
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The service area 10 of the system shown in Figure 1A is provided with a center point 12. There are three types of installation paths provided within the system or service area 10 as is shown in Fig. 1B. The distribution paths 30a are of the shortest length and extend from the center point 12 to the four innermost distribution points 22a, only one of which is shown for clarity. Within the installation paths 30a are contained only feeder lines 20. Branching out from the distribution points 22a, are the second type of installation paths 31 that contain feeder lines 20 and subscriber lines 25. Finally, within each distribution area 15, there are installation paths 32 for just the subscriber lines 25, both of which are indicated by hyphens or dashes between the subscriber stations 16.
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The inner four distribution areas 15 have two sections of installation paths 31 that accommodate both feeder and subscriber lines or cables. The direction along which installation paths 31 extend is in alignment with the subscriber stations so that both the subscriber lines 25 for a particular distribution area and the feeder lines 20 for that distribution area as well as the subscriber lines for the adjacent distribution area, for example, adjacent in the extending direction of the feeder lines 20, are accommodated in one installation path 31. Further, the distribution point 22a for each of the distribution areas 15 having the two installation paths 31 contained therein are located at an intersection of the two installation paths. In this way, the total network installation path length of the network is reduced in comparison to that of the installation path network shown in Figure 2, representing a conventional system.
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The total length of the installation path network in Figure 1 can be determined from adding the installation path lengths for installation paths 31 and 32 in addition to the installation path sections 30a and 30b that accommodate just feeder lines. In particular, there is one row and four columns of subscriber lines 25 housed in either one or the other of the subscriber line installation paths 32 and combined feeder and subscriber installation paths 31 in a distribution area 15. Combined, these installation paths provide a total length of 3/4 x 5 x 16 = 60. The installation paths 30b, are for feeder lines only. Feeder line installation paths 30b extend across one quarter unit dimension, and there are 12 such sections producing a combined length of three units. Lastly, there are four diagonally extending feeder line installation path sections 30a that are √2/2 in unit dimension, thus providing for a total unit length of approximately 0.7 units. Accordingly, the total installation path length for the network of the system distribution area 10 is 63.7 units of measure, compared with 75 units of measure for the installation path network for the system shown in Figure 2.
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In Figure 1B, an alternative embodiment for the route topology of the feeder installation paths is shown. In addition to the installation paths 30a for only the feeder lines, there are still two combined feeder and subscriber line installation paths 31 for an inner quadrant distribution area 15 have different positions as compared with the positions shown in Figure 1A, but the intersection of the two installation paths still provides the location of the distribution point 22 for that distribution area.
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For purposes of discussion, the subdivided distribution areas 15 are shown as being square areas, but any shape that is required to properly subdivide the system area 10 can be used as long as the distribution point for each of the areas is nearest to the center point 12 for the overall system area. Further, although the connection of subscriber stations 16 is shown in Figures 1A and 1B to be like that shown in Figure 3A for each distribution area 15, the subscriber station connections, i.e., the topology of the subscriber lines 25, can be changed according to Figures 3B - 3E without changing the above given estimation of total length of the installation path network. Further, the subscriber lines 25 can be arranged like that shown in Figure 3F if required, wherein subscriber lines 25' and the corresponding installation paths 32' extend diagonally through the distribution area. For the topology of Fig. 3F, the estimate of total length of the installation path network would be increased with respect to that for the other embodiments.
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In Figures 5A - 5G, additional modifications to the subscriber line connections of subscriber stations 16 to the distribution point are shown. In the connection representations shown in Figure 5A - 5G, it is determined that certain subscriber stations 16a need to be connected to the distribution system initially, whereas other subscriber stations 16b will be connected later, or not at all, depending upon the circumstances. Thus, the modifications shown in Figures 5A - 5G represent initial connections of subscriber stations that can be achieved upon initial installation of the system and which allow connection of other subscriber stations at a later time by merely stringing a subscriber line from one subscriber station in use to an adjacent station in order to bring the adjacent subscriber station on line.
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In particular, the modification to the route topology shown in Fig. 5G provides an installation path for the subscriber lines that is preferred for aerial installations. The subscriber lines 25a extend between adjacent rows of the subscriber stations 16, while subscriber lines 25b leading therefrom extend to each of the individual stations that are connected to the system.
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In Figure 7A, a representative distribution area having thirty-six planned subscriber stations is shown. Figure 7A shows that predetermined ones of the subscriber stations 16a that are to be initially connected to the system are connected to the distribution point 22 through subscriber lines whereas the remainder of the planned subscriber stations are not yet connected, but are easily connected to an adjacent subscriber station when needed in the future. By the configuration shown in Figure 7A, only one subscriber line between adjacent subscriber stations is required in order to bring one of the subscriber stations not initially connected on line. In Figure 7B, the diagram shows that although subscriber stations are not regularly placed, subscriber stations can be connected to the distribution point.
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Figure 4A-4C shows another embodiment of the invention wherein the system area 10 to be serviced by the installation path network includes a center point 12 and a plurality of subdivided distribution areas 45. The distribution areas 45 are not square, as in the first embodiment of the invention.
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The feeder lines are connected to the distribution areas 45 through feeder line installation paths 30 and combined feeder and subscriber installation paths 31 as with the other embodiments. In each distribution area 45, the distribution point is positioned in the distribution area at a location overlaying or superimposed on the subscriber station nearest to the center point 12. The subscriber stations 16 are connected by subscriber lines 25 that follow subscriber line only installation paths 32.
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In Figures 4B and 4C, alternative configurations of the subscriber line connections, for example the topology of the subscriber lines 25 is shown. The distribution point 12 is shown to be located in the lower left hand corner, and although it is not shown, the distribution point is positioned nearest to the center point 12 of the distribution system area.
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In Figure 6, an embodiment of the invention similar to that shown in Figure 4A is shown. Like reference numerals indicate like features of the system area that is shown. The difference between the Figure 6 embodiment and the Figure 4 embodiments of the present invention is that the terminal distribution point 42 within distribution areas 45 is positioned midway between two rows of subscriber station 16, rather than in a position superimposed on the distribution station nearest to the center point 12 of the distribution system area as in the other embodiments.
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According to the embodiment of Fig. 6, as in the embodiment of Fig. 5G, mutually shared subscriber lines 25b extend between adjacent rows of subscriber stations 16 with individual subscriber lines 25a extending therefrom to the respective distribution stations. The embodiment of the invention in Figure 6 includes the possibility that the installation paths for the feeder lines 25b that accommodate both the feeder lines and the subscriber lines are buried, whereas the installation paths 25a are disposed in an aerial configuration with subscriber lines 25 aerially connected to each of the subscriber stations 16. According to the topology of this embodiment, the subscriber lines 25a can be aerially dropped from the mutually shared subscriber lines 25b.
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While preferred embodiments of the invention have been shown and described with reference to the drawings, additional modifications and embodiments of the invention are contemplated to be within the scope of the invention, as defined by the claims.
